How to Check and Properly Set Suspension Sag on Your Motorcycle | Slacker Sag Tool Makes It Easy!

Understanding and adjusting the suspension sag on your motorcycle is crucial for improving your ride quality, safety, and handling. Many riders overlook or don’t regularly check their suspension sag, often because they aren’t sure how to do it or think it requires a second person. This guide will walk you through everything you need to know about setting sag, regardless of whether you’re riding a street bike, adventure bike, or dirt bike. Plus, I’ll introduce you to a tool that simplifies the process so you can do it entirely on your own—the Slacker Sag Tool. (see video below)

What is Suspension Sag?

Suspension sag is the amount your motorcycle settles or “squats” under its own weight and your weight (including passengers and luggage) when you sit on it. Setting the proper sag is essential because it determines where your suspension will sit within its travel range, allowing it to absorb impacts effectively and create an overall great ride.

Why Proper Sag is Important

Every suspension system is designed with a set amount of travel (usually measured in millimeters). For optimal performance, about one-third of this travel should be set as sag. Setting the correct sag:

• Allows your suspension to move up and down without bottoming out or topping out.
• Keeps your wheels on the ground, ensuring traction, especially over obstacles or uneven surfaces.
• Maintains the correct geometry of your motorcycle for optimal handling.

If your sag is set incorrectly, you risk poor handling and traction, which can be dangerous when encountering obstacles, potholes, or rough terrain.

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Understanding Sag and Preload

When adjusting your sag, you may also hear the term “preload.” Although they work together, preload is simply the adjustment you make on your suspension to set your desired sag. Some manufacturers, like Harley-Davidson, provide a guideline based on rider and passenger weight, which can help you get close, but fine-tuning is essential to match your specific riding setup.

Measuring Suspension Sag: Tools and Methods

You can measure sag using a basic tape measure, a Motion Pro Sag Scale, or a Slacker Digital Sag Tool. Let’s go over each:

1. Tape Measure Method (Old School)

• This method requires two people, one to hold the bike and the other to measure.
• Use the tape measure to note the suspension height with no weight, then again with the rider seated. The difference is your sag measurement.

While simple, this method can be imprecise due to human error, maintaining the correct angle, and some math involved.

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2. Motion Pro Folding Sliding Sag Scale

• This tool offers a sliding scale in millimeters, making it easier to get a more accurate reading.
• It requires two people.
• It has an axle bolt pin for maintaining a proper and precise measurement. 
• Set the scale on your axle bolt and take readings by lifting the bike, then letting it settle with the rider on board.

3. Slacker Digital Sag Tool

• My personal favorite for ease and accuracy, allowing a one-person operation.
• The tool auto-zeros and provides a digital readout of your sag, removing any guesswork.
• You can also use a Bluetooth remote or app to see the sag measurement on your phone or handlebars, which is especially helpful for fine-tuning on your own.

Step-By-Step Guide to Measuring Sag with the Slacker Digital Sag Tool

1. Attach the Slacker Tool:
   • For most bikes, attach the tool magnetically to your axle nut.
   • Run the tool’s string to a fixed point above (such as your frame) to measure the travel accurately.
2. Zero the Tool:
   • Lift the bike’s rear wheel to unload the suspension. The Slacker tool will auto-zero.
   • Let the bike settle back down on its suspension.
3. Mount and Measure:
   • Get on the bike, with both feet on the footpegs or floorboards, and bounce up and down to let the suspension settle.
   • Note the sag reading displayed on the remote or app—this is your sag measurement.
4. Adjusting Sag:
   • If your sag isn’t within the recommended range (around 25 mm for my Harley touring model), adjust the preload on your shocks and remeasure until you reach the desired sag.

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Example: Calculating the Sag Range (1/3 of your total suspension travel should be your sag)

For example, on my Harley-Davidson Street Glide with 3 inches of rear travel:

• Convert 3 inches to millimeters (3 in x 25.4 mm = 76.2 mm).
  • There are 25.4 mm in an inch
• Divide by three (76.2 mm ÷ 3 ≈ 25 mm).
• Aim for 25 mm of sag.

Different motorcycles will have varied travel distances and, consequently, different sag settings. My Husqvarna TE300 sag setting is around 110 mm.

My Recommended Suspension Setup

For my Harley-Davidson Street Glide, I use the Wilbers LDC Nivomat Suspension System, which I’ve reviewed extensively. This suspension automatically adjusts itself based on load, so once it’s set, it recalibrates on the go to maintain the correct sag as I add or remove weight (e.g., passengers or luggage). It’s incredibly stable, and I highly recommend it for Harley touring bikes. You can find this suspension setup in the Law Abiding Biker Store where we offer customized ordering and support.

Conclusion

Setting sag on your motorcycle is an essential maintenance step for all riders, whether you’re hitting the road, trail, or track. While you can do it with basic tools, investing in a tool like the Slacker Digital Sag Tool makes the process more accurate and saves time. Proper sag ensures your motorcycle handles optimally, increasing safety and ride quality.

For more resources, check out our in-depth suspension videos and guides, including my full review on the Wilbers LDC Nivomat suspension. And if you’re ready to take your ride to the next level, explore our store for high-quality motorcycle parts and accessories!